1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly to a liquid crystal display panel and a fabricating method thereof that are capable of simplifying the manufacturing process of an upper substrate by reducing the number of masks and also simplifying the manufacturing process of making spacers at desired locations.
2. Description of the Background Art
Generally, a liquid crystal display (LCD) controls the light transmittance of liquid crystal cells in response to video signals to thereby display a picture corresponding to the video signals on a liquid crystal display panel. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix form, and driving circuits for driving the liquid crystal panel.
LCDs are generally classified into two modes, according to the direction of the electric field driving the liquid crystal—a twisted nematic (TN) mode using a vertical electric field and an in-plane switching (IPS) mode using a horizontal electric field. LCDs of TN mode drive the liquid crystal by the vertical electric field formed between the common electrode and the pixel electrode facing the upper substrate. LCDs of TN mode have the advantage of high aperture ratios, but have the disadvantage of narrow viewing angles. LCDs of IPS mode drive the liquid crystal by the horizontal electric field formed between the pixel electrode and the common electrode located in parallel on the lower substrate. LCDs of IPS mode have the advantage of wide viewing angles, but have the disadvantage of low aperture ratios.
FIG. 1 is a cross-sectional view illustrating an IPS mode liquid crystal display panel of the background art.
Referring to FIG. 1, the IPS Mode liquid crystal display panel includes: an upper plate having a black matrix 2, a color filter 6, a planarization layer 7, a pattern spacer 13, and an upper alignment layer 8, which are sequentially formed on an upper substrate 1 a rear surface of which is covered with materials (not shown) forming a transparent electrode for preventing static electricity; a lower plate having a thin film transistor (TFT), a common electrode 4, a pixel electrode 9, and a lower alignment layer 10, which are respectively formed on a lower substrate 5; and a liquid crystal(not shown) injected into the inner space between the upper and the lower plates.
In the upper plate, the black matrix 2 is formed so as to overlap with the area of the TFT on the lower substrate 5 and with the area (not shown) of gate and data lines, and partitions the cell regions at which the color filter 6 is to be formed. The black matrix 20 functions to prevent light leakage and absorb external light, to thereby improve the contrast ratio. The color filter 6 is formed so as to encompass the cell region partitioned by the black matrix 2. The color filter 6 is formed by separate red (R), green (G), and blue (B) filters and realizes red, green, and blue colors. The planarization layer 7 is formed to cover the color filter and planarizes the upper substrate 1. The patterned spacer 13 maintains the cell gap between the upper substrate 1 and the lower substrate 5.
In the lower plate, the TFT includes: a gate electrode 16 along with a gate line (not shown) formed on the lower substrate 5; semiconductor layers 126 and 127 formed to overlap with the gate electrode 16 and a gate insulating layer 129 therebetween; and source/drain electrodes 128 and 130 formed along with a data line (not shown) on both the semiconductor layers 126 and 127 therebetween. In response to scan signals from the gate line, this TFT supplies pixel signals from the data line to the pixel electrode 9. The pixel electrode 9 is made from transparent conductive materials with high light transmittance, and makes contact with the drain electrode 130 of the TFT through a protective film 25. The common electrode 4 is formed in a stripe form so as to alternate with the pixel electrode 9. A common voltage, the reference to the drive of the liquid crystal, is applied to the common electrode 4. The horizontal electric field formed by this common voltage and the voltage supplied to the pixel electrode 9 makes the liquid crystal rotate horizontally. The upper and lower alignment layers 8, 10 for aligning the liquid crystal are formed through a two-stage process which includes application of alignment materials such as polyimide, which is then followed by rubbing.
FIGS. 2a to 2f are cross-sectional views illustrating the steps for fabricating the upper substrate adopting the IPS mode.
Referring to FIG. 2a, opaque materials such as nontransparent metal or nontransparent resin are deposited on the upper substrate 1. Then, the nontransparent materials are patterned through a photolithography process and an etching process using a first mask. Consequently, black matrixes 2 are formed.
Referring to FIG. 2b, red resin (R) is deposited on the upper substrate 1 having the black matrix formed thereon. Then, the red resin (R) is patterned through a photolithography process and an etching process using a second mask. Consequently, a red color filter (3R) is formed.
Referring to FIG. 2c, green resin (G) is deposited on the upper substrate 1 having the red color filter (3R) formed thereon. Then, the green resin (G) is patterned through a photolithography process and an etching process using the third mask. Consequently, a green color filter (3G) is formed.
Referring to FIG. 2d, blue resin (B) is deposited on the upper substrate 1 having the green color filter (3G) formed thereon. Then, the blue resin (G) is patterned through a photolithography process and an etching process using a fourth mask. Consequently, a blue color filter (3B) is formed.
Referring to FIG. 2e, planarization materials are deposited on the entire surface of the upper substrate 1 having the red, green, and blue color filters (6) formed thereon. Consequently, the planarization layer 7 is formed.
Referring to FIG. 2f, spacer materials are deposited on the upper substrate 1 having the planarization layer 7 formed thereon. Then, the spacer materials are patterned through a photolithography process and an etching process using a fifth mask. Consequently, the pattern spacer is formed. In this process, organic materials are used for the spacer material.
The pattern spacer 13 of the background art LCD occupies about 2% of the area of the upper substrate 1. More than 95% of the spacer material that has been printed on the entire surface of the upper substrate 1 to form the pattern spacer 13 is removed during the processes of exposure, development, and etching. As a result, the cost of materials is high and the fabrication costs are high. Further, the mask process for forming the pattern spacer 13 includes a plurality of sub-processes such as deposition, cleaning, photolithography, etching, stripping, and inspection. This complex fabricating process leads to the problem of increases in the manufacturing costs of a background art liquid crystal panel.
In order to solve the problems mentioned, an ink-jet device is used to make spacers as shown in FIG. 3a and FIG. 3b. 
First of all, as shown in FIG. 3a, an ink-jet device 40 is aligned on the upper substrate 1 having the planarization layer formed thereon, wherein the planarization layer is overlapped with the position of the black matrix 2. Then, the spacer material 26a is jetted to the planarization layer 7 from the ink-jet device 40. Here, organic materials are used for the spacer material. The spacer 55 formed through this ink-jet device thereafter undergoes an exposure to ultraviolet radiation from a light source 59 or a firing process as shown in FIG. 3b, resulting in the width (W) and height (H) as shown.
During the formation of the spacer using the background art ink-jet device, the spacer material (of low viscosity) is subjected to gravity while being jetted to the planarization layer 7. Due to gravity, the spacer material spreads out widely on the planarization layer 7 upon being applied thereto. This causes a problem in which spacers are formed at undesirable locations, that is, locations which do not overlap with the black matrix 2 such as the display areas.